Flexible printed circuit boards and flexible cables constructed from polymeric film, (e.g.) polyester or polyimide film, substrates are generally known in the art. Such films are lightweight, flexible and thin. Varying circuit shapes, dimensions, circuit arrangements and different length cable arrangements may be constructed using polyester. However, a disadvantage to the use of polyester is its relatively low tolerance to heat. Lap joints have been formed using a hot bar to cause solder reflow on polyimide substrates, but using a similar process with a polyester substrate could burn or melt polyester. Unfortunately, polyimides are substantially more expensive than polyesters.
When electrical connection was desired between printed circuit boards, cables were often used having a sufficient number of wire leads to connect the bond pads on one circuit to another circuit. Such electrical connections were most commonly made by inserting the cable structure into a mechanical plug-in formed on the edge of one circuit. Such plug-ins provided excellent electrical and mechanical bonding. However, they were expensive to make and difficult to install during assembly. The plug-in type edge bonding connectors replaced complex point-to-point connections using discrete copper wires.
Flexible circuit boards have been joined electrically (and physically) either by using anisotropic adhesives (which are electrically conductive in the vertical or z-direction, but are substantially electrically insulating in the horizontal x, y, or x-y plane) or by physically crimping the boards together. Unfortunately, adhesives require a relatively large surface area to ensure adequate conductivity. In addition, mechanical crimps can be prone to failure and have limited conductivity.
Conventional circuit board assemblies and methods of their construction do not appear to provide an economical and reliable solution to interconnection and construction challenges. Therefore, a printed circuit board assembly comprising a flexible circuit member and method for connecting a printed circuit board to such a flexible member that addresses the above-identified deficiencies is a demonstrable goal in this art.